Basil Rathbone
Sherlock Holmes

Nigel Bruce
Dr. John Watson

Hillary Brooke
Lydia Marlowe

Henry Daniell
Professor James Moriarty

Paul Cavanagh
Sir George Fenwick

Matthew Boulton
Inspector Gregson

Eve Amber
Maude Fenwick

Frederick Worlock
Dr. Onslow

Percival Vivian
Dr. Simnell

Coulter Irwin
Corporal Williams

Sally Shepherd
Crandon

Mary Gordon
Mrs. Hudson

John Burton
Waring the Mesmerist (uncredited)

Harold De Becker
Shoelace Vendor Henchman (uncredited)

Tony Ellis
Carter the Hypnotized Subject (uncredited)

Bess Flowers
Bar Patron (seen in mirror) (uncredited)

Kay Harding
4th Victim (uncredited)

Alec Harford
Commissioner of the CID (uncredited)

Olaf Hytten
Fenwick's Butler Norris (uncredited)

Boyd Irwin
Short-Tempered Officer Closing Window (uncredited)